Update license for RT-Thread kernel.

1. Add signal implementation;
2. Change the 'rt_uint8_t' of cmd to 'int';

modify：     ../../libcpu/risc-v/e310/stack.c
	rmove unused macro definition
modify：     ../../src/idle.c
	Return to the original version

	add file that forget to submit before
	auto change timer mtimercmp register on the base of RT_TICK_PER_SECOND in rtconfig.h
	no flashing led
new file：   ../../src/idle.c
	recover old file

	enable interrupt after return form rt_hw_context_switch

The rt_list_isempty has prototype of "int rt_list_isempty(const rt_list_t *l)".
So the compiler has a good reason that the rt_thread_defunct list does
not change within rt_thread_idle_excute thus optimize the "while" loop
into a "if".

So add the volatile qualifier when test against the rt_thread_defunc list.

Out side world is difficult to tell whethere there is dead thread
remaining. If rt_thread_idle_excute only do one cleanup, it's hard to
finish cleanups outside the idle thread. So let is loop and do all the
cleanups in one call.

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2554 bbd45198-f89e-11dd-88c7-29a3b14d5316

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2503 bbd45198-f89e-11dd-88c7-29a3b14d5316

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2458 bbd45198-f89e-11dd-88c7-29a3b14d5316

using rt_bool_t instead of rt_err_t

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2150 bbd45198-f89e-11dd-88c7-29a3b14d5316

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2119 bbd45198-f89e-11dd-88c7-29a3b14d5316

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2044 bbd45198-f89e-11dd-88c7-29a3b14d5316

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2005 bbd45198-f89e-11dd-88c7-29a3b14d5316

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@1998 bbd45198-f89e-11dd-88c7-29a3b14d5316

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@1739 bbd45198-f89e-11dd-88c7-29a3b14d5316

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@1715 bbd45198-f89e-11dd-88c7-29a3b14d5316